Switching control optimisation strategy of segmented transmitting coils for on-road charging of electrical vehicles

Resonant wireless power transfer presents the opportunity of on-road charging of electrical vehicles. In this study, a system with controllable square transmitting coils in series is proposed. Circuit model of multiple transmitting coils is first built to derive unified resonant condition of primary side and receiving power of secondary side. On the basis of numerical analysis of mutual inductance in a system without control strategy and transmitter spacing are fixed, receiving power variations along with the number of energised transmitting coils and horizontal misalignment between transmitting and receiving devices are further investigated. Taking power demand, receiving power fluctuation requirement and switching frequency of transmitting coils into consideration, this study presents an optimal switching control strategy of transmitting coils based on the width-variable window searching method. With the proposed strategy in this study, the switching frequency is reduced while the power demand and the power fluctuation requirement can be satisfied simultaneously. The theoretical analysis is confirmed by experimental results.